Photomask blank, photomask blank processing method, and photomask blank manufacturing method

Abstract

To provide a photomask blank including a silicon-containing hard mask film which can function as a hard mask when an absorber layer is processed by dry etching, and can contribute to improvement in resolution of a resist pattern.SOLUTION: A photomask blank includes a substrate, a multilayer reflective film layer formed on the substrate and reflecting EUV light, an absorber layer formed on the multilayer reflective film layer and absorbing EUV light, a silicon-containing hard mask film formed directly or indirectly on the absorber layer, and a photoresist film formed on the silicon-containing hard mask film, wherein the silicon-containing hard mask film is a cured product of a composition for forming a silicon-containing hard mask film that is cured at a temperature of 50°C or more and 180°C or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photomask blank, which is a material for producing a photomask and has a hard mask film used when etching a thin film formed on a substrate, a method for processing a photomask blank using the same, and a method for manufacturing the same. [Background technology]

[0002] With the miniaturization of semiconductor devices, currently, an exposure method is used in which a pattern is transferred onto a wafer using a photomask with an optical projection exposure apparatus that uses an ArF excimer laser. However, because exposure methods using these optical projection exposure apparatuses will eventually reach their resolution limit, new pattern formation methods such as direct writing using electron beam lithography, imprint lithography, and EUV lithography have been proposed.

[0003] Among these new lithography technologies, EUV exposure, which is considered the ultimate in shortening the wavelength of ultraviolet exposure, uses EUV light with a wavelength of approximately 13.5 nm, which is even shorter than that of excimer lasers, and typically reduces the exposure time to approximately one-quarter. This technology is attracting attention as a next-generation lithography technology for semiconductor devices. Because refractive optics cannot be used in EUV exposure due to the short wavelength, reflective optics are used, and reflective masks have been proposed (Patent Document 1). The reflective film (multilayer reflective film layer) with a multilayer structure used in the reflective mask is typically a multilayer film in which films of materials with relatively high refractive indexes and films of materials with relatively low refractive indexes are alternately stacked on the order of several nanometers. For example, a multilayer film in which thin films of silicon and thin films of molybdenum are alternately stacked is known to have high reflectivity for 13-14 nm EUV light.

[0004] In forming a photomask pattern, for example, a composite substrate is formed on the substrate, which has a multilayer reflective film layer on the substrate, a capping layer on the multilayer reflective film layer to prevent oxidation and act as a protective layer during mask cleaning, a buffer layer on the buffer layer to prevent etching damage during mask pattern formation, an absorber layer on the buffer layer to absorb EUV light, and a hard mask layer on the buffer layer that is resistant to etching of the absorber layer. A photoresist film is formed on the composite substrate to produce a photomask blank. The photoresist film on the photomask blank is subjected to pattern exposure with an electron beam, followed by development to obtain a resist pattern. The absorber layer is then etched using the obtained resist pattern as a mask to form an absorber layer pattern. However, when miniaturizing the absorber layer pattern, if the photoresist film thickness is maintained at the same level as before miniaturization, the ratio of film thickness to the pattern, or the so-called aspect ratio, increases, which deteriorates the photoresist pattern shape, resulting in poor pattern transfer and, in some cases, causing the resist pattern to collapse or peel. Therefore, it is necessary to thin the resist film thickness as miniaturization progresses.

[0005] On the other hand, for the absorber layer that is etched using a resist pattern as a mask, materials that are used include, for example, Ta-based materials such as Ta, TaB, TaBN, TaO, and TaN, and materials that are Cr-based and contain at least one component selected from N, O, and C. When etching materials that are primarily Ta, chlorine-based dry etching can be used to pattern them, and when etching materials that are primarily Cr, fluorine-based dry etching can be used. However, for the reasons mentioned above, etching absorber layers using thin resists is no longer able to ensure sufficient processing accuracy when forming mask patterns for use in EUV exposure. For this reason, it is necessary to form a hard mask layer under the photoresist film.

[0006] Although it is not a processing method for reflective photomask blanks, Patent Document 2 discloses that, for example, in order to dry-etch a light-shielding film made of a silicon-based material with a thin resist, a film of a chromium-based material that is thin enough to function as a hard mask can be used as a hard mask film, thereby enabling high precision in the resulting mask pattern. Similarly, Patent Document 3 discloses that a silicon-based material film can be used as a hard mask for a chromium-based light-shielding film.

[0007] Furthermore, as a method for forming a hard mask by alternately forming films of a chromium-based material, which is generally processed under chlorine-based dry etching conditions, and a material containing a transition metal and silicon, which is generally processed under fluorine-based dry etching conditions, as described above, it has been proposed to use an SOG film as a hard mask film when processing a chromium-based material film (Patent Document 4).

[0008] When an SOG film is used as a hard mask film, it is necessary to perform a high-temperature bake treatment after coating the SOG film to harden the SOG film and prevent mixing with the photoresist film. For example, in the examples of Patent Document 4, a bake treatment is performed at 190°C. However, the processing method for reflective photomask blanks equipped with a multilayer reflective film layer does not mention whether an SOG film can be used as a hard mask, and its practical use as an EUV photomask blank is unclear. One reason for this is presumably that, in reflective photomask blanks, when the SOG film is hardened, the multilayer reflective film layer laminated below the SOG film is also subjected to high temperatures, which disrupts the periodic structure of the multilayer reflective film layer, resulting in a decrease in the reflectivity of EUV light and the generation of phase defects.

[0009] In the examples of Patent Document 5, a phase shift film is formed on a quartz substrate, and a light-shielding layer is formed thereon to prepare a mask blank, and a silicon-containing composition is spin-coated and baked at 250°C to form a silicon-containing film. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 63-201656 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-241060 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-146152 [Patent Document 4] Japanese Patent Application Laid-Open No. 2008-26500 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-230986 Summary of the Invention [Problem to be solved by the invention]

[0011] As mentioned above, further improvement in the precision of reflective photomask technology requires the ability to transfer resist patterns to absorber layers with higher precision. The use of SOG films as hard mask films is useful from the viewpoint of compensating for the lack of dry etching resistance of thin-film photoresists and improving the pattern resolution of photoresists, but the suppression of mixing with photoresists and interlayer mixing of multilayer reflective film layers remains an issue.

[0012] The present invention has been made in view of the above circumstances, and has an object to provide a photomask blank including a silicon-containing hard mask film that can function as a hard mask when processing an absorber layer by dry etching and can also contribute to improving the resolution of a resist pattern, a method for processing a photomask blank using the same, and a method for manufacturing the photomask blank. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention provides a photomask blank, comprising: A substrate; a multilayer reflective film layer formed on the substrate and reflecting EUV light; an absorber layer formed on the multilayer reflective film layer to absorb the EUV light; a silicon-containing hard mask film formed directly or indirectly on the absorber layer; a photoresist film formed on the silicon-containing hard mask film; Equipped with The photomask blank is characterized in that the silicon-containing hard mask film is a cured product of a silicon-containing hard mask film-forming composition that cures at a temperature of 50°C or higher and 180°C or lower.

[0014] Such photomask blanks contain a silicon-containing hard mask film useful as a hard mask film, allowing for highly accurate transfer of a fine resist pattern to the absorber layer. Furthermore, since the silicon-containing hard mask film can be formed within the above temperature range, the transfer accuracy of the resist pattern can be improved without inducing interlayer mixing of the multilayer reflective film layer. In other words, by using the photomask blanks of the present invention, a photomask can be provided that includes an absorber layer on which a fine pattern is formed with high accuracy without degrading the reflectivity of EUV light. In other words, the photomask blanks of the present invention are photomask blanks that contain a silicon-containing hard mask film that can function as a hard mask when processing the absorber layer by dry etching and can also contribute to improving the resolution of the resist pattern.

[0015] Furthermore, the silicon-containing hard mask film-forming composition preferably contains a silicon-containing compound having at least one of a repeating unit represented by the following general formula (Sx-1), a repeating unit represented by the following general formula (Sx-2), and a partial structure represented by the following general formula (Sx-3): [ka] (In the formula, R a , R b , and R c are each a monovalent organic group having 1 to 30 carbon atoms, which may be the same or different.

[0016] Such a silicon-containing hard mask film-forming composition has excellent thermosetting properties, and thus a cured film can be formed by baking at a temperature of 50°C or higher and 180°C or lower. Furthermore, a silicon-containing hard mask film with excellent dry etching resistance can be formed. Therefore, a photomask blank containing a cured product of such a silicon-containing hard mask-forming composition can provide a photomask including an absorber layer on which a fine pattern is formed with high precision.

[0017] In this case, in the above formulas (Sx-1) to (Sx-3), R a ~R c At least one of the groups is preferably an organic group having one or more carbon-oxygen single bonds or carbon-oxygen double bonds.

[0018] A silicon-containing hard mask film-forming composition containing such a silicon-containing compound having an organic group has excellent thermosetting properties, and can form a cured film by baking at a temperature of 50°C or higher and 180°C or lower.

[0019] It is preferable that the silicon-containing hard mask film-forming composition further contains a crosslinking catalyst.

[0020] Such a silicon-containing hard mask film-forming composition has even better thermosetting properties, and therefore can reliably form a cured film by baking at a temperature of 50°C or higher and 180°C or lower.

[0021] The crosslinking catalyst is preferably a sulfonium salt, an iodonium salt, a phosphonium salt, an ammonium salt, an alkali metal salt, or a polysiloxane having any of a sulfonium salt, an iodonium salt, a phosphonium salt, and an ammonium salt as part of its structure.

[0022] Such a silicon-containing hard mask film-forming composition has particularly excellent thermosetting properties, and therefore can more reliably form a cured film by baking at a temperature of 50°C or higher and 180°C or lower.

[0023] The present invention also provides a method for processing photomask blanks, comprising the steps of: (i-1) a step of irradiating the photomask blank of the present invention with an electron beam and then developing it with a developer to form a photoresist pattern on the photoresist film; (i-2) forming the silicon-containing film pattern on the silicon-containing hard mask film by etching using the photoresist pattern as a mask; (i-3) directly or indirectly processing the absorber layer by etching using the silicon-containing film pattern as a mask; The present invention provides a method for processing a photomask blank, comprising:

[0024] This photomask blank processing method uses a silicon-containing hard mask film, which has better dry etching resistance to chlorine-based gases than a photoresist film, as a hard mask, allowing the resist pattern to be transferred to the absorber layer of the photomask blank with high accuracy. Furthermore, since the silicon-containing hard mask film can be formed at a temperature range of 50°C to 180°C, the transfer accuracy of the resist pattern can be improved without inducing interlayer mixing in the multilayer reflective film layer. In other words, the photomask blank processing method of the present invention can provide a photomask including an absorber layer on which a fine pattern is formed with high accuracy without degrading the reflectivity of EUV light.

[0025] The present invention also provides a method for producing a photomask blank, comprising the steps of: providing a substrate; forming a multilayer reflective film layer that reflects EUV light on the substrate; forming an absorber layer on the multilayer reflective film layer to absorb the EUV light; a step of directly or indirectly applying a silicon-containing hard mask film-forming composition onto the absorber layer, the composition being cured at a temperature of 50°C or higher and 180°C or lower, to obtain a coating film, and curing the coating film at a temperature of 50°C or higher and 180°C or lower, to form a silicon-containing hard mask film; forming a photoresist film on the silicon-containing hard mask film; The present invention provides a method for producing a photomask blank, comprising:

[0026] Such a method for producing a photomask blank can form a silicon-containing hard mask film useful as a hard mask film, thereby producing a photomask blank that can transfer a fine resist pattern to an absorber layer with high accuracy. Furthermore, by forming the silicon-containing hard mask film within the above temperature range, the transfer accuracy of the resist pattern can be improved without inducing interlayer mixing of the multilayer reflective film layer. In other words, the method for producing a photomask blank of the present invention can provide a photomask blank that can form a fine pattern in an absorber layer with high accuracy without degrading the reflectivity of EUV light. [Effects of the Invention]

[0027] As described above, by using the photomask blank of the present invention, a photomask having an absorber layer on which a fine pattern is formed with high precision can be provided without deteriorating the reflectance of EUV light. That is, the photomask blank of the present invention is a photomask blank including a silicon-containing hard mask film that can function as a hard mask when processing the absorber layer by dry etching and can also contribute to improving the resolution of the resist pattern.

[0028] Furthermore, according to the method for processing photomask blanks of the present invention, it is possible to provide a photomask having an absorber layer on which a fine pattern is formed with high precision without deteriorating the reflectance of EUV light.

[0029] Furthermore, the method for producing a photomask blank of the present invention makes it possible to produce a photomask blank that allows a fine pattern to be formed in the absorber layer with high precision without deteriorating the reflectance of EUV light. [Brief explanation of the drawings]

[0030] [Figure 1]1 is a schematic cross-sectional view of an example of a photomask blank of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] As described above, further improvements in the precision of reflective photomask technology require the ability to transfer resist patterns to absorber layers with higher precision. The use of SOG films as hard mask films is useful in compensating for the lack of dry etching resistance of thin-film photoresists (Patent Document 4) and is also expected to improve the pattern resolution of photoresists. However, it is unclear whether SOG films can be used as hard masks in processing methods for reflective photomasks with multilayer reflective film layers. Furthermore, when curing an SOG film in a reflective photomask, high temperatures are also applied to the multilayer reflective film stacked below the SOG film, disrupting the periodic structure of the multilayer reflective film. This is thought to be a problem, as it can reduce the reflectivity of EUV light and cause phase defects.

[0032] The present inventors have been searching for and intensively studying photomask blanks in which a resist pattern is transferred to an absorber layer with high accuracy, a method for processing photomask blanks, and a method for manufacturing photomask blanks. As a result, they have found that by using a cured product formed from a silicon-containing hard mask film-forming composition that cures at a temperature of 50°C or higher and 180°C or lower as a hard mask, the transfer accuracy of a resist pattern to an absorber layer can be improved without inducing interlayer mixing of a multilayer reflective film layer, and have completed the present invention.

[0033] That is, the present invention provides a photomask blank, A substrate; a multilayer reflective film layer formed on the substrate and reflecting EUV light; an absorber layer formed on the multilayer reflective film layer to absorb the EUV light; a silicon-containing hard mask film formed directly or indirectly on the absorber layer; a photoresist film formed on the silicon-containing hard mask film; Equipped with The photomask blank is characterized in that the silicon-containing hard mask film is a cured product of a silicon-containing hard mask film-forming composition that is cured at a temperature of 50°C or higher and 180°C or lower.

[0034] The photomask blanks, photomask blank processing methods, and photomask blank manufacturing methods of the present invention use a hard mask formed from a cured product using a silicon-containing hard mask film-forming composition that can be cured at a temperature of 50° C. or higher and 180° C. or lower, and therefore can improve the transfer accuracy of a resist pattern to an absorber layer without inducing interlayer mixing in a multilayer reflective film layer. In other words, the present invention can provide photomask blanks that can realize a photomask including an absorber layer on which a fine pattern is formed with high precision without degrading the reflectivity of EUV light, and is therefore extremely useful in fine patterning for semiconductor device manufacturing.

[0035] The present invention will be described in detail below, but the present invention is not limited thereto.

[0036] <Photomask blanks> First, the structures of the reflective photomask blank and reflective photomask of the present invention will be described below with reference to the drawings. In the description of the drawings, the same components are given the same reference symbols and their description may be omitted. Furthermore, the drawings may be enlarged for convenience, and the dimensional ratios of the components may not necessarily be the same as in reality.

[0037] In this specification, the hardening of the silicon-containing hard mask film-forming composition means that when a photoresist material is applied onto the silicon-containing hard mask film, the amount of film reduction of the silicon-containing hard mask film is small and mixing with the photoresist film does not occur. In this case, the amount of film reduction of the silicon-containing hard mask film is preferably less than 5% of the film thickness before application of the photoresist material, more preferably less than 3%, even more preferably less than 1%, and particularly preferably less than 0.5%.

[0038] [Overall structure of photomask blanks] The photomask blank (reflective mask blank) of the present invention generally includes a substrate, a multilayer reflective film layer formed on the substrate (e.g., on one main surface (front surface) of the substrate) that reflects EUV light (exposure light), an absorber layer (light absorbing film) formed on the multilayer reflective film layer, a silicon-containing hard mask film formed directly or indirectly on the absorber layer, and a photoresist film formed on the silicon-containing hard mask film. The photomask blank may further include an etching mask film that functions as an etching mask when processing the absorber film. In addition, a back conductive film may be provided on the other main surface (back surface) of the substrate. The photomask blank may also include a protective film.

[0039] 1 is a schematic cross-sectional view showing an example of a photomask blank (reflective photomask blank) of the present invention. This reflective photomask blank 101 includes a substrate 1, a multilayer reflective film layer 2 formed on and in contact with the substrate 1, which reflects exposure light, i.e., EUV light, a protective film 3 (optional in the present invention) formed on and in contact with the multilayer reflective film layer 2 for protecting the multilayer reflective film layer 2, an absorber layer (light-absorbing film) 4 formed on and in contact with the protective film 3 for absorbing exposure light, a first layer 5 (optional in the present invention) of a hard mask film formed on and in contact with the absorber layer 4, which functions as a hard mask when patterning the absorber layer 4 by dry etching, a silicon-containing hard mask film 6 which functions as a second layer of the hard mask when patterning the first layer 5 of the hard mask film by dry etching, and a photoresist film 7 formed on and in contact with the silicon-containing hard mask film 6.

[0040] Each of the constituent members (essential members and optional members) of the photomask blank of the present invention will be described in detail below.

[0041] [substrate] The substrate preferably has low thermal expansion characteristics, for example, a thermal expansion coefficient of ±2×10 -8 It is preferable that the substrate be made of a material having a temperature within a range of 0.5 nm / °C. Examples of such materials include titania-doped quartz glass (SiO2-TiO2 glass). In addition, it is preferable that the surface roughness of the main surface of the substrate is 0.5 nm or less in terms of RMS value.

[0042] [Backside conductive film] A conductive film (back surface conductive film) used to electrostatically chuck the reflective photomask to an exposure device (e.g., an EUV scanner) may be provided on the other main surface (back surface) of the substrate, which is the surface opposite to the one main surface.

[0043] The back surface conductive film preferably has a sheet resistance of 100 Ω / □ or less, and there are no particular restrictions on the material. Examples of materials for the back surface conductive film include materials containing tantalum (Ta) or chromium (Cr). They may also contain oxygen (O), nitrogen (N), etc. The thickness of the back surface conductive film is not particularly limited as long as it functions as an electrostatic chuck, but is usually about 20 to 300 nm.

[0044] [Multilayer reflective film layer] The multilayer reflective film layer is a film in a reflective mask that reflects EUV light, which is exposure light. The multilayer reflective film has a periodic stacking structure in which, for example, high-refractive index layers with a relatively high refractive index to the exposure light and low-refractive index layers with a relatively low refractive index to the exposure light are alternately stacked.

[0045] The high refractive index layer is preferably formed of a material containing silicon (Si), and the low refractive index layer is preferably formed of a material containing molybdenum (Mo). The thickness of the multilayer reflective film layer is preferably 270 nm or more and 400 nm or less.

[0046] [Protective film] The optional protective film is also called a capping film. The protective film is a film for protecting the multilayer reflective film layer. The protective film is preferably formed of a material containing ruthenium (Ru), and may further contain titanium (Ti), zirconium (Zr), niobium (Nb), etc. It may also contain oxygen (O), nitrogen (N), carbon (C), etc. The thickness of the protective film is not particularly limited, but is preferably 2 nm or more and 5 nm or less.

[0047] [Absorbent layer] The absorber layer (light absorbing film) may be made of any material that absorbs EUV light and can be patterned. The material for the absorber layer is not particularly limited, but is preferably, for example, a film containing tantalum (Ta), which may further contain oxygen (O), nitrogen (N), boron (B), etc. The film thickness of the absorber layer is not particularly limited, but is preferably 50 nm or more and 80 nm or less.

[0048] [First layer of hard mask film] The first layer of the hard mask film, which is an optional configuration for the present invention, is a layer that can function as an etching mask (hard mask) in etching the absorber layer.

[0049] The first layer of the hard mask film is preferably made of a material that is resistant to fluorine-based dry etching of the absorber layer and can be removed by chlorine-based dry etching. The first layer of the hard mask film is preferably formed of a material containing chromium (Cr). In addition to chromium, it may contain one or more elements selected from oxygen (O), nitrogen (N), and carbon (C), and a material consisting of chromium and one or more elements selected from oxygen, nitrogen, and carbon is more preferred. It is preferable that the hard mask film contains nitrogen, and chromium nitride (CrN) consisting of chromium and nitrogen is particularly suitable. It is also preferable that the hard mask film contains oxygen together with nitrogen, and chromium oxide nitride (CrNO) consisting of chromium, nitrogen, and oxygen is particularly suitable.

[0050] Furthermore, carbon may be contained in addition to nitrogen and oxygen, and when carbon is contained, chromium nitride oxide carbide (CrNOC) consisting of chromium, nitrogen, oxygen, and carbon is suitable. The thickness of the etching mask film is not particularly limited, but is preferably 5 nm or more and 20 nm or less.

[0051] [Silicon-containing hard mask film (second layer of hard mask film)] The silicon-containing hard mask film (second layer of the hard mask film) of the present invention is, for example, a layer that can function as an etching mask (hard mask) when etching the first layer of the hard mask film. When used as an etching mask when etching the first layer of the hard mask film, the silicon-containing hard mask film (second layer of the hard mask film) is preferably made of a material that is resistant to chlorine-based dry etching of the first layer of the hard mask film and can be removed by fluorine-based dry etching. The silicon-containing hard mask film (second layer of the hard mask film) is a cured product of a composition containing silicon (Si), in other words, it is formed from a material containing silicon (Si). The silicon-containing material may contain one or more elements selected from oxygen (O), nitrogen (N), and carbon (C) in addition to silicon, and is more preferably a material consisting of silicon and one or more elements selected from oxygen, nitrogen, and carbon.

[0052] In the present invention, the silicon-containing hard mask film (second layer of the hard mask film) is a cured product of a silicon-containing hard mask film-forming composition that cures at a temperature of 50° C. to 180° C. In particular, it is preferably a cured product (silicon oxide-based material film) obtained by applying (A) a silicon-containing hard mask film-forming composition containing a silicon-containing compound having at least one of a repeating unit represented by the following general formula (Sx-1), a repeating unit represented by the following general formula (Sx-2), and a partial structure represented by the following general formula (Sx-3), and baking the applied composition at a temperature of 50° C. to 150° C.

[0053] [ka] (In the formula, R a , R b and R c are each a monovalent organic group having 1 to 30 carbon atoms, which may be the same or different.

[0054] If the silicon-containing hard mask film is a cured product of a composition that cures at a temperature higher than 180°C, the reflectivity of the multilayer reflective film layer will decrease. On the other hand, if the silicon-containing hard mask film is a cured product of a composition that cures at a temperature lower than 50°C, even when stored in the product's usage environment (e.g., a clean room at 23°C), a portion of the film will cure, causing defects.

[0055] The silicon-containing hard mask film-forming composition (A) preferably contains polysiloxane (Sx) and a solvent, and may further contain additives such as a crosslinking catalyst and a crosslinking agent.

[0056] The silicon-containing hard mask film-forming composition (A) contains the following: That Each possible component will now be described in more detail.

[0057] (Polysiloxane (Sx)) The polysiloxane (Sx) preferably contains one or more of a repeating unit represented by the following general formula (Sx-1), a repeating unit represented by the following general formula (Sx-2), and a partial structure represented by the following general formula (Sx-3).

[0058] [ka] (In the formula, R a , R b , and R c are each a monovalent organic group having 1 to 30 carbon atoms, which may be the same or different.

[0059] The polysiloxane (Sx) may be a thermally crosslinkable polysiloxane (Sx).

[0060] The thermally crosslinkable polysiloxane (Sx) can be produced by hydrolyzing and condensing the following hydrolyzable monomer (Sm).

[0061] Specific examples of the hydrolyzable monomer (Sm) include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, trimethoxysilane, triethoxysilane, tripropoxysilane, triisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltrippropoxysilane, ethyltriisopropoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane. ethoxysilane, vinyltrippropoxysilane, vinyltriisopropoxysilane, propyltrimethoxysilane, propyltriethoxysilane, propyltrippropoxysilane, propyltriisopropoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, isopropyltrippropoxysilane, isopropyltriisopropoxysilane, butyltrimethoxysilane, butyltriethoxysilane, butyltrippropoxysilane, butyltriisopropoxysilane, sec-butyltrimethoxysilane, sec-butyltriisopropoxysilane Iethoxysilane, sec-butyltrippropoxysilane, sec-butyltriisopropoxysilane, t-butyltrimethoxysilane, t-butyltriethoxysilane, t-butyltrippropoxysilane, t-butyltriisopropoxysilane, cyclopropyltrimethoxysilane, cyclopropyltriethoxysilane, cyclopropyltrippropoxysilane, cyclopropyltriisopropoxysilane, cyclobutyltrimethoxysilane, cyclobutyltriethoxysilane, cyclobutyltrippropoxysilane, cyclobutyltriisopropoxy Sisilane, cyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, cyclopentyltrippropoxysilane, cyclopentyltriisopropoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, cyclohexyltrippropoxysilane, cyclohexyltriisopropoxysilane, cyclohexenyltrimethoxysilane, cyclohexenyltriethoxysilane, cyclohexenyltrippropoxysilane, cyclohexenyltriisopropoxysilane, cyclohexenylethyltrimethoxysilane,Cyclohexenylethyltriethoxysilane, cyclohexenylethyltripropoxysilane, cyclohexenylethyltriisopropoxysilane, cyclooctyltrimethoxysilane, cyclooctyltriethoxysilane, cyclooctyltripropoxysilane, cyclooctyltriisopropoxysilane, cyclopentadienylpropyltrimethoxysilane, cyclopentadienylpropyltriethoxysilane, cyclopentadienylpropyltripropoxysilane, cyclopentadienylpropyltriisopropoxysilane, bicycloheptenyl Trimethoxysilane, bicycloheptenyltriethoxysilane, bicycloheptenyltrippropoxysilane, bicycloheptenyltriisopropoxysilane, bicycloheptyltrimethoxysilane, bicycloheptyltriethoxysilane, bicycloheptyltrippropoxysilane, bicycloheptyltriisopropoxysilane, adamantyltrimethoxysilane, adamantyltriethoxysilane, adamantyltrippropoxysilane, adamantyltriisopropoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane Tripropoxysilane, phenyltriisopropoxysilane, benzyltrimethoxysilane, benzyltriethoxysilane, benzyltripropoxysilane, benzyltriisopropoxysilane, anisyltrimethoxysilane, anisyltriethoxysilane, anisyltrippropoxysilane, anisyltriisopropoxysilane, tolyltrimethoxysilane, tolyltriethoxysilane, tolyltrippropoxysilane, tolyltriisopropoxysilane, phenethyltrimethoxysilane, phenethyltriethoxysilane, phenethyltrippropoxysilane , phenethyltriisopropoxysilane, naphthyltrimethoxysilane, naphthyltriethoxysilane, naphthyltripropoxysilane, naphthyltriisopropoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, dimethyldipropoxysilane, dimethyldiisopropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldipropoxysilane, diethyldiisopropoxysilane, dipropyldimethoxysilane, dipropyldiethoxysilane,Dipropyl dipropoxysilane, dipropyl diisopropoxysilane, diisopropyl dimethoxysilane, diisopropyl diethoxysilane, diisopropyl dipropoxysilane, diisopropyl diisopropoxysilane, dibutyl dimethoxysilane, dibutyl diethoxysilane, dibutyl dipropoxysilane, dibutyl diisopropoxysilane, di-sec-butyl dimethoxysilane, di-sec-butyl diethoxysilane, di-sec-butyl dipropoxysilane, di-sec-butyl diisopropoxysilane, di-t-butyl dimethoxysilane, di t-butyldiethoxysilane, di-t-butyldipropoxysilane, di-t-butyldiisopropoxysilane, dicyclopropyldimethoxysilane, dicyclopropyldiethoxysilane, dicyclopropyldipropoxysilane, dicyclopropyldiisopropoxysilane, dicyclobutyldimethoxysilane, dicyclobutyldiethoxysilane, dicyclobutyldipropoxysilane, dicyclobutyldiisopropoxysilane, dicyclopentyldimethoxysilane, dicyclopentyldiethoxysilane, dicyclopentyldipropoxysilane, dicyclopentyldiisopropoxysilane Dicyclohexyldiisopropoxysilane, Dicyclohexyldimethoxysilane, Dicyclohexyldiethoxysilane, Dicyclohexyldipropoxysilane, Dicyclohexyldiisopropoxysilane, Dicyclohexenyldimethoxysilane, Dicyclohexenyldiethoxysilane, Dicyclohexenyldipropoxysilane, Dicyclohexenyldiisopropoxysilane, Dicyclohexenylethyldimethoxysilane, Dicyclohexenylethyldiethoxysilane, Dicyclohexenylethyldipropoxysilane, Dicyclohexenylethyldiisopropoxysilane bis(bicycloheptenyl)dimethoxysilane, dicyclooctyldiethoxysilane, dicyclooctyldipropoxysilane, dicyclooctyldiisopropoxysilane, dicyclopentadienylpropyldimethoxysilane, dicyclopentadienylpropyldiethoxysilane, dicyclopentadienylpropyldipropoxysilane, dicyclopentadienylpropyldiisopropoxysilane, bis(bicycloheptenyl)dimethoxysilane, bis(bicycloheptenyl)diethoxysilane, bis(bicycloheptenyl)dipropoxysilane,Bis(bicycloheptenyl)diisopropoxysilane, bis(bicycloheptyl)dimethoxysilane, bis(bicycloheptyl)diethoxysilane, bis(bicycloheptyl)dipropoxysilane, bis(bicycloheptyl)diisopropoxysilane, diadamantyldimethoxysilane, diadamantyldiethoxysilane, diadamantyldipropoxysilane, diadamantyldiisopropoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, methylphenyldi Examples include methoxysilane, methylphenyldiethoxysilane, diphenyldipropoxysilane, diphenyldiisopropoxysilane, trimethylmethoxysilane, trimethylethoxysilane, dimethylethylmethoxysilane, dimethylethylethoxysilane, dimethylphenylmethoxysilane, dimethylphenylethoxysilane, dimethylbenzylmethoxysilane, dimethylbenzylethoxysilane, dimethylphenethylmethoxysilane, and dimethylphenethylethoxysilane.

[0062] The hydrolyzable monomer (Sm) is preferably tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, cyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxy ... Examples include cyclohexenyltrimethoxysilane, cyclohexenyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, benzyltrimethoxysilane, benzyltriethoxysilane, phenethyltrimethoxysilane, phenethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, methylethyldimethoxysilane, methylethyldiethoxysilane, dipropyldimethoxysilane, dibutyldimethoxysilane, methylphenyldimethoxysilane, methylphenyldiethoxysilane, trimethylmethoxysilane, dimethylethylmethoxysilane, dimethylphenylmethoxysilane, dimethylbenzylmethoxysilane, and dimethylphenethylmethoxysilane.

[0063] The above R corresponding to the compounds exemplified above as the hydrolyzable monomer (Sm) a , R b and R cAnother example of the organic group represented by the formula (Sm-R) is an organic group having one or more carbon-oxygen single bonds or carbon-oxygen double bonds. Specifically, it is an organic group having one or more groups selected from the group consisting of an ether bond, an ester bond, an alkoxy group, a hydroxy group, and the like. An example of this is an organic group represented by the following general formula (Sm-R). The inclusion of such an organic group improves thermosetting properties, making it suitable for the photomask blanks of the present invention. Furthermore, it improves adhesion to the overlying photoresist film, allowing for the formation of a highly rectangular resist pattern after development.

[0064] [ka] In the general formula (Sm-R), P represents a hydrogen atom, a cyclic ether group, a hydroxyl group, an alkoxy group having 1 to 4 carbon atoms, an alkylcarbonyloxy group having 1 to 6 carbon atoms, or an alkylcarbonyl group having 1 to 6 carbon atoms; and Q1, Q2, Q3, and Q4 each independently represent -C q H (2q-p) P p - (wherein P is the same as above, p is an integer of 0 to 3, and q is an integer of 0 to 10 (provided that q=0 represents a single bond), u is an integer of 0 to 3, and S1 and S2 each independently represent -O-, -CO-, -OCO-, -COO-, or -OCOO-. v1, v2, and v3 each independently represent 0 or 1. T is a divalent group selected from the group consisting of a divalent atom other than carbon, an alicyclic ring, an aromatic ring, or a heterocyclic ring. Examples of T as an alicyclic ring, an aromatic ring, or a heterocyclic ring which may contain a heteroatom such as an oxygen atom are shown below. The position of T to which Q2 and Q3 are bonded is not particularly limited, but can be appropriately selected taking into consideration reactivity due to steric factors, the availability of commercially available reagents used in the reaction, and the like.)

[0065] [ka]

[0066] Preferred examples of the organic group having one or more carbon-oxygen single bonds or carbon-oxygen double bonds in the general formula (Sm-R) include the following: In the following formula, (Si) is written to indicate the bonding site with Si.

[0067] [ka]

[0068] [ka]

[0069] Also, R a , R b , and R c As examples of the organic group, an organic group containing a silicon-silicon bond can also be used. Specific examples include the following:

[0070] [ka]

[0071] Also, R a , R b , and R c Examples of the organic group include organic groups having a protecting group that is decomposed by an acid. Specific examples include the organic groups listed in paragraphs

[0043] to

[0048] of JP-A-2013-167669 and the organic groups obtained from silicon compounds listed in paragraph

[0056] of JP-A-2013-224279.

[0072] Furthermore, R a , R b , and R c As an example of the organic group, an organic group having a fluorine atom can also be used. Specific examples include organic groups obtained from silicon compounds shown in paragraphs

[0059] to

[0065] of JP 2012-53253 A.

[0073] The hydrolyzable monomer (Sm) has one, two or three hydrolyzable groups such as chlorine, bromine, iodine, acetoxy, methoxy, ethoxy, propoxy or butoxy groups bonded to the silicon atom represented by (Si) in the partial structure.

[0074] [Method for synthesizing thermally crosslinkable polysiloxane (Sx)] (Synthesis Method 1: Method using an acid catalyst) The thermally crosslinkable polysiloxane (Sx) used in the present invention can be produced, for example, by hydrolyzing and condensing one type of hydrolyzable monomer (Sm) or a mixture of two or more types of hydrolyzable monomers (Sm) in the presence of an acid catalyst.

[0075] Examples of the acid catalyst used in this step include organic acids such as formic acid, acetic acid, oxalic acid, maleic acid, methanesulfonic acid, benzenesulfonic acid, and toluenesulfonic acid, and inorganic acids such as hydrofluoric acid, hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, perchloric acid, and phosphoric acid. The amount of catalyst used is 1 × 10 per mole of monomer. -6 ~10 moles, preferably 1 x 10 -5 ~5 moles, more preferably 1 x 10 -4 ~1 mole.

[0076] When obtaining a thermally crosslinkable polysiloxane (Sx) from these monomers by hydrolysis and condensation, the amount of water added is preferably 0.01 to 100 mol, more preferably 0.05 to 50 mol, and even more preferably 0.1 to 30 mol per mol of hydrolyzable substituent bonded to the monomer. If the amount is 100 mol or less, the apparatus used for the reaction can be small and economical.

[0077] One example of the operation method is to add a monomer to an aqueous catalyst solution to initiate the hydrolysis condensation reaction. At this time, an organic solvent may be added to the aqueous catalyst solution, or the monomer may be diluted with an organic solvent, or both may be performed. The reaction temperature is 0 to 100°C, preferably 5 to 50°C. A preferred method is to maintain the temperature at 5 to 50°C during the dropwise addition of the monomer, and then mature the mixture at 20 to 50°C.

[0078] Preferred organic solvents that can be added to the aqueous catalyst solution or that can be used to dilute the monomer include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, acetone, acetonitrile, tetrahydrofuran, toluene, hexane, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methyl amyl ketone, butanediol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, butanediol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, t-butyl propionate, propylene glycol mono t-butyl ether acetate, γ-butyrolactone, and mixtures thereof.

[0079] Among these solvents, water-soluble ones are preferred. Examples include alcohols such as methanol, ethanol, 1-propanol, and 2-propanol; polyhydric alcohols such as ethylene glycol and propylene glycol; polyhydric alcohol condensate derivatives such as butanediol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, butanediol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, butanediol monopropyl ether, propylene glycol monopropyl ether, and ethylene glycol monopropyl ether; acetone, acetonitrile, and tetrahydrofuran. Among these, solvents having a boiling point of 100° C. or less are particularly preferred.

[0080] The amount of organic solvent used is preferably 0 to 1,000 ml, particularly 0 to 500 ml, per mole of monomer. A smaller amount of organic solvent used allows for a smaller reaction vessel, which is more economical.

[0081] Thereafter, if necessary, a neutralization reaction of the catalyst is carried out to obtain an aqueous reaction mixture. At this time, the amount of alkaline substance that can be used for neutralization is preferably 0.1 to 2 equivalents relative to the acid used in the catalyst. This alkaline substance may be any substance that exhibits alkaline properties in water.

[0082] Subsequently, by-products such as alcohol produced in the hydrolysis condensation reaction are preferably removed from the reaction mixture by vacuum removal or the like. The temperature to which the reaction mixture is heated depends on the types of organic solvent added and alcohol produced in the reaction, but is preferably 0 to 100°C, more preferably 10 to 90°C, and even more preferably 15 to 50°C. The degree of vacuum varies depending on the types of organic solvent and alcohol to be removed, the exhaust device, the condenser, and the heating temperature, but is preferably atmospheric pressure or less, more preferably 80 kPa or less absolute pressure, and even more preferably 50 kPa or less absolute pressure. While it is difficult to accurately determine the amount of alcohol removed, it is desirable to remove approximately 80 mass% or more of the produced alcohol.

[0083] Next, the acid catalyst used in the hydrolysis and condensation may be removed from the reaction mixture. To remove the acid catalyst, water and the thermally crosslinkable polysiloxane solution are mixed, and the thermally crosslinkable polysiloxane is extracted with an organic solvent. The organic solvent used here is preferably one that can dissolve the thermally crosslinkable polysiloxane and separates into two layers when mixed with water. Examples of the solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, acetone, tetrahydrofuran, toluene, hexane, ethyl acetate, cyclohexanone, methyl amyl ketone, butanediol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, butanediol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, butanediol monopropyl ether, propylene glycol monopropyl ether, ethylene glycol monopropyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, t-butyl acetate, t-butyl propionate, propylene glycol mono t-butyl ether acetate, γ-butyrolactone, methyl isobutyl ketone, cyclopentyl methyl ether, and mixtures thereof.

[0084] Furthermore, a mixture of a water-soluble organic solvent and a poorly water-soluble organic solvent can also be used. For example, a methanol-ethyl acetate mixture, an ethanol-ethyl acetate mixture, a 1-propanol-ethyl acetate mixture, a 2-propanol-ethyl acetate mixture, a butanediol monomethyl ether-ethyl acetate mixture, a propylene glycol monomethyl ether-ethyl acetate mixture, an ethylene glycol monomethyl ether-ethyl acetate mixture, a butanediol monoethyl ether-ethyl acetate mixture, a propylene glycol monoethyl ether-ethyl acetate mixture, an ethylene glycol monoethyl ether-ethyl acetate mixture, a butanediol monopropyl ether-ethyl acetate mixture, a propylene glycol monopropyl ether-ethyl acetate mixture, an ethylene glycol monopropyl ether-ethyl acetate mixture, a methanol-methyl isobutyl ketone mixture, an ethanol-methyl isobutyl ketone mixture, a 1-propanol-methyl isobutyl ketone mixture, a 2-propanol-methyl isobutyl ketone mixture, a propylene glycol monomethyl ether-methyl isobutyl ketone mixture, an ethylene glycol monomethyl ether-methyl isobutyl ketone mixture, ton mixture, propylene glycol monoethyl ether-methyl isobutyl ketone mixture, ethylene glycol monoethyl ether-methyl isobutyl ketone mixture, propylene glycol monopropyl ether-methyl isobutyl ketone mixture, ethylene glycol monopropyl ether-methyl isobutyl ketone mixture, methanol-cyclopentyl methyl ether mixture, ethanol-cyclopentyl methyl ether mixture, 1-propanol-cyclopentyl methyl ether mixture, 2-propanol-cyclopentyl methyl ether mixture, propylene glycol monomethyl ether-cyclopentyl methyl ether mixture, ethylene glycol monomethyl ether-cyclopentyl methyl ether mixture, propylene glycol monoethyl ether-cyclopentyl methyl ether mixture, ethylene glycol monoethyl ether-cyclopentyl methyl ether mixture, propylene glycol monopropyl ether-cyclopentyl methyl ether mixture, ethylene glycol monopropyl ether-cyclopentyl methyl ether mixture,Preferred combinations include, but are not limited to, a methanol-propylene glycol methyl ether acetate mixture, an ethanol-propylene glycol methyl ether acetate mixture, a 1-propanol-propylene glycol methyl ether acetate mixture, a 2-propanol-propylene glycol methyl ether acetate mixture, a propylene glycol monomethyl ether-propylene glycol methyl ether acetate mixture, an ethylene glycol monomethyl ether-propylene glycol methyl ether acetate mixture, a propylene glycol monoethyl ether-propylene glycol methyl ether acetate mixture, an ethylene glycol monoethyl ether-propylene glycol methyl ether acetate mixture, a propylene glycol monopropyl ether-propylene glycol methyl ether acetate mixture, and an ethylene glycol monopropyl ether-propylene glycol methyl ether acetate mixture.

[0085] The mixing ratio of the water-soluble organic solvent to the poorly water-soluble organic solvent is appropriately selected, but is usually 0.1 to 1,000 parts by mass, preferably 1 to 500 parts by mass, and more preferably 2 to 100 parts by mass of the water-soluble organic solvent per 100 parts by mass of the poorly water-soluble organic solvent.

[0086] Subsequently, washing with neutral water may be performed. This water may be what is commonly called deionized water or ultrapure water. The amount of water used is preferably 0.01 to 100 L, more preferably 0.05 to 50 L, and even more preferably 0.1 to 5 L per 1 L of the thermally crosslinkable polysiloxane solution. This washing method involves placing both components in the same container, stirring, and then allowing the mixture to stand to separate the aqueous layer. Washing may be performed once or more, but washing 10 or more times does not necessarily provide the desired effect, so washing is preferably performed approximately 1 to 5 times.

[0087] Other methods for removing the acid catalyst include a method using an ion exchange resin and a method of neutralizing the acid catalyst with an epoxy compound such as ethylene oxide or propylene oxide and then removing the acid catalyst. These methods can be appropriately selected depending on the acid catalyst used in the reaction.

[0088] This water washing operation may cause a portion of the thermally crosslinkable polysiloxane to escape into the aqueous layer, thereby providing an effect substantially equivalent to that of the fractionation operation. Therefore, the number of water washes and the amount of washing water may be appropriately selected in consideration of the catalyst removal effect and the fractionation effect.

[0089] In both the thermally crosslinkable polysiloxane solution containing the residual acid catalyst and the thermally crosslinkable polysiloxane solution from which the acid catalyst has been removed, the desired thermally crosslinkable polysiloxane solution is obtained by adding a final solvent and performing solvent exchange under reduced pressure. The temperature for solvent exchange depends on the types of reaction solvent and extraction solvent to be removed, but is preferably 0 to 100°C, more preferably 10 to 90°C, and even more preferably 15 to 50°C. The degree of vacuum varies depending on the type of extraction solvent to be removed, the exhaust device, the condenser, and the heating temperature, but is preferably atmospheric pressure or less, more preferably 80 kPa or less absolute pressure, and even more preferably 50 kPa or less absolute pressure.

[0090] In this case, the change in solvent may cause the thermally crosslinkable polysiloxane to become unstable. This occurs due to the compatibility between the final solvent and the thermally crosslinkable polysiloxane. To prevent this, a monohydric, dihydric, or polyhydric alcohol having a cyclic ether as a substituent, as described in paragraphs

[0181] and

[0182] of JP 2009-126940 A, may be added as a stabilizer. The amount added is 0 to 25 parts by mass, preferably 0 to 15 parts by mass, and more preferably 0 to 5 parts by mass, per 100 parts by mass of the thermally crosslinkable polysiloxane in the solution before solvent exchange. However, if added, 0.5 parts by mass or more is preferred. If necessary, a monohydric, dihydric, or polyhydric alcohol having a cyclic ether as a substituent can be added to the solution before solvent exchange before performing the solvent exchange operation.

[0091] If the thermally crosslinkable polysiloxane is concentrated beyond a certain concentration, the condensation reaction may proceed further, causing the polysiloxane to become insoluble in organic solvents. Therefore, it is preferable to keep the polysiloxane in a solution state of a moderate concentration. If the polysiloxane is too diluted, the amount of solvent required will be excessive, so it is economical to keep the polysiloxane in a solution state of a moderate concentration. The concentration in this case is preferably 0.1 to 20% by mass.

[0092] The final solvent to be added to the thermally crosslinkable polysiloxane solution is preferably an alcohol-based solvent, and particularly preferably a monoalkyl ether derivative such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, or butanediol. Specifically, butanediol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, butanediol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, butanediol monopropyl ether, propylene glycol monopropyl ether, ethylene glycol monopropyl ether, or diacetone alcohol is preferred.

[0093] If these solvents are the main component, it is also possible to add a non-alcoholic solvent as an auxiliary solvent, such as acetone, tetrahydrofuran, toluene, hexane, ethyl acetate, cyclohexanone, methyl amyl ketone, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, t-butyl acetate, t-butyl propionate, propylene glycol mono-t-butyl ether acetate, γ-butyrolactone, methyl isobutyl ketone, or cyclopentyl methyl ether.

[0094] Another reaction procedure using an acid catalyst is to add water or a water-containing organic solvent to a monomer or an organic solution of the monomer to initiate the hydrolysis reaction. In this case, the catalyst may be added to the monomer or the organic solution of the monomer, or may be added to the water or the water-containing organic solvent. The reaction temperature is 0 to 100°C, preferably 10 to 50°C. A preferred method is to heat the mixture to 10 to 50°C during the dropwise addition of water, and then to raise the temperature to 20 to 50°C for aging.

[0095] When an organic solvent is used, it is preferably a water-soluble one, and examples thereof include polyhydric alcohol condensate derivatives such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, acetone, tetrahydrofuran, acetonitrile, butanediol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, butanediol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, butanediol monopropyl ether, propylene glycol monopropyl ether, ethylene glycol monopropyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and propylene glycol monopropyl ether, and mixtures thereof.

[0096] The amount of organic solvent used is preferably 0 to 1,000 ml, particularly 0 to 500 ml, per mole of monomer. A smaller amount of organic solvent used is more economical, since it allows for a smaller reaction vessel. The resulting reaction mixture can be post-treated in the same manner as described above to obtain a thermally crosslinkable polysiloxane.

[0097] (Synthesis method 2: Method using an alkaline catalyst) The thermally crosslinkable polysiloxane (Sx) can also be produced by hydrolyzing and condensing one or a mixture of two or more hydrolyzable monomers (Sm) in the presence of an alkali catalyst.

[0098] Examples of the alkali catalyst used here include methylamine, ethylamine, propylamine, butylamine, ethylenediamine, hexamethylenediamine, dimethylamine, diethylamine, ethylmethylamine, trimethylamine, triethylamine, tripropylamine, tributylamine, cyclohexylamine, dicyclohexylamine, monoethanolamine, diethanolamine, dimethylmonoethanolamine, monomethyldiethanolamine, triethanolamine, diazabicyclooctane, diazabicyclocyclononene, diazabicycloundecene, hexamethylenetetramine, aniline, N,N-dimethylaniline, pyridine, N,N-dimethylaminopyridine, pyrrole, piperazine, pyrrolidine, piperidine, picoline, tetramethylammonium hydroxide, choline hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, etc. The amount of catalyst used is 1 × 10 per mole of silicon monomer. -6 mol to 10 mol, preferably 1 × 10 -5 mol to 5 mol, more preferably 1×10 -4 mol to 1 mol.

[0099] When obtaining a thermally crosslinkable polysiloxane from the above monomers by hydrolysis and condensation, the amount of water added is preferably 0.1 to 50 moles per mole of hydrolyzable substituent bonded to the monomer. If the amount is 50 moles or less, the apparatus used for the reaction can be made smaller, which is more economical.

[0100] One example of the operation method is to add a monomer to an aqueous catalyst solution to initiate the hydrolysis condensation reaction. At this time, an organic solvent may be added to the aqueous catalyst solution, or the monomer may be diluted with an organic solvent, or both may be performed. The reaction temperature is 0 to 100°C, preferably 5 to 50°C. A preferred method is to maintain the temperature at 5 to 50°C during the dropwise addition of the monomer, and then mature the mixture at 20 to 50°C.

[0101] As the organic solvent that can be added to the aqueous alkali catalyst solution or that can dilute the monomer, the same organic solvents as those exemplified as those that can be added to the aqueous acid catalyst solution are preferably used. The amount of organic solvent used is preferably 0 to 1,000 ml per mole of monomer, in order to carry out the reaction economically.

[0102] Thereafter, if necessary, a neutralization reaction of the catalyst is carried out to obtain an aqueous reaction mixture. At this time, the amount of the acidic substance that can be used for neutralization is preferably 0.1 to 2 equivalents relative to the alkaline substance used in the catalyst. This acidic substance may be any substance that is acidic in water.

[0103] Subsequently, by-products such as alcohol produced in the hydrolysis-condensation reaction are preferably removed from the reaction mixture by vacuum removal or the like. The temperature to which the reaction mixture is heated depends on the type of organic solvent added and the type of alcohol produced in the reaction, but is preferably 0 to 100°C, more preferably 10 to 90°C, and even more preferably 15 to 50°C. The degree of vacuum varies depending on the type of organic solvent and alcohol to be removed, the exhaust device, the condenser, and the heating temperature, but is preferably atmospheric pressure or less, more preferably 80 kPa or less absolute pressure, and even more preferably 50 kPa or less absolute pressure. While it is difficult to accurately determine the amount of alcohol removed, it is desirable to remove approximately 80 mass% or more of the produced alcohol.

[0104] Next, to remove the alkali catalyst used in the hydrolysis and condensation, the thermally crosslinkable polysiloxane is extracted with an organic solvent. The organic solvent used here is preferably one that can dissolve the thermally crosslinkable polysiloxane and separates into two layers when mixed with water. Examples of the solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, acetone, tetrahydrofuran, toluene, hexane, ethyl acetate, cyclohexanone, methyl amyl ketone, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol monopropyl ether, ethylene glycol monopropyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, t-butyl acetate, t-butyl propionate, propylene glycol mono t-butyl ether acetate, γ-butyrolactone, methyl isobutyl ketone, cyclopentyl methyl ether, and mixtures thereof.

[0105] Furthermore, it is also possible to use a mixture of a water-soluble organic solvent and a slightly water-soluble organic solvent.

[0106] Specific examples of organic solvents that can be used to remove the alkali catalyst include the organic solvents specifically exemplified above as those that can be used to remove the acid catalyst, and mixtures of water-soluble organic solvents and water-insoluble organic solvents.

[0107] The mixing ratio of the water-soluble organic solvent to the poorly water-soluble organic solvent is appropriately selected, but is usually 0.1 to 1,000 parts by mass, preferably 1 to 500 parts by mass, and more preferably 2 to 100 parts by mass of the water-soluble organic solvent per 100 parts by mass of the poorly water-soluble organic solvent.

[0108] Next, the mixture is washed with neutral water. This water may be what is commonly called deionized water or ultrapure water. The amount of water used is 0.01 to 100 L, preferably 0.05 to 50 L, and more preferably 0.1 to 5 L, per 1 L of the thermally crosslinkable polysiloxane solution. This washing method involves placing both in the same container, stirring, and then leaving the mixture to stand to separate the aqueous layer. The number of washes may be one or more times, but washing 10 or more times does not necessarily provide the desired effect, so the number of washes is preferably about 1 to 5 times.

[0109] The final solvent is added to the washed thermally crosslinkable polysiloxane solution, and solvent exchange is performed under reduced pressure to obtain the desired thermally crosslinkable polysiloxane solution. The temperature for solvent exchange depends on the type of extraction solvent to be removed, but is preferably 0 to 100°C, more preferably 10 to 90°C, and even more preferably 15 to 50°C. The degree of vacuum varies depending on the type of extraction solvent to be removed, the exhaust device, the condenser, and the heating temperature, but is preferably atmospheric pressure or less, more preferably 80 kPa or less absolute, and even more preferably 50 kPa or less absolute.

[0110] The final solvent to be added to the thermally crosslinkable polysiloxane solution is preferably an alcohol solvent, and particularly preferred are monoalkyl ethers such as ethylene glycol, diethylene glycol, and triethylene glycol, and monoalkyl ethers such as propylene glycol and dipropylene glycol.Specifically, preferred are propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol monopropyl ether, ethylene glycol monopropyl ether, diacetone alcohol, etc.

[0111] Another reaction procedure using an alkali catalyst is to add water or an aqueous organic solvent to the monomer or an organic solution of the monomer to initiate the hydrolysis reaction. In this case, the catalyst may be added to the monomer or the organic solution of the monomer, or may be added to the water or aqueous organic solvent in advance. The reaction temperature is 0 to 100°C, preferably 10 to 50°C. A preferred method is to heat the mixture to 10 to 50°C during the dropwise addition of water, and then to raise the temperature to 20 to 50°C for aging.

[0112] The organic solvent that can be used as the organic solution of the monomer or the aqueous organic solvent is preferably a water-soluble one, and examples thereof include polyhydric alcohol condensate derivatives such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, acetone, tetrahydrofuran, acetonitrile, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol monopropyl ether, ethylene glycol monopropyl ether, propylene glycol dimethyl ether, diethylene glycol dimethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and propylene glycol monopropyl ether, and mixtures thereof.

[0113] The molecular weight of the thermally crosslinkable polysiloxane obtained by synthesis method 1 or 2 can be adjusted not only by selecting the monomer but also by controlling the reaction conditions during polymerization. However, it is preferable to use one with a weight-average molecular weight of 100,000 or less, more preferably 200 to 50,000, and even more preferably 300 to 30,000. A weight-average molecular weight of 100,000 or less prevents the generation of foreign matter or coating spots. The data regarding the weight-average molecular weight above was measured by gel permeation chromatography (GPC) using RI as a detector and tetrahydrofuran as an eluent, and polystyrene as a standard substance, and the molecular weight was expressed in terms of polystyrene.

[0114] (Crosslinking catalyst) The silicon-containing hard mask film-forming composition may further contain one or more crosslinking catalysts. Examples of crosslinking catalysts that can be added include compounds represented by the following general formula (Xc0). By including such a crosslinking catalyst, the thermosetting properties can be further improved. L a H b A (Xc0) (In the formula, L is lithium, sodium, potassium, rubidium, cesium, sulfonium, iodonium, phosphonium, or ammonium. A is a non-nucleophilic counter ion. a is an integer of 1 or more, b is an integer of 0 or 1 or more, and a+b is the valence of the non-nucleophilic counter ion.)

[0115] Specific examples of the compound represented by general formula (Xc0) used in the present invention as a crosslinking catalyst include sulfonium salts of the following general formula (Xc-1), iodonium salts of the following general formula (Xc-2), phosphonium salts of the following general formula (Xc-3), ammonium salts of the following general formula (Xc-4), alkali metal salts, and polysiloxanes (Xc-10) having ammonium salts, sulfonium salts, phosphonium salts, or iodonium salts as part of their structure. Specifically, materials described in paragraphs

[0124] to

[0163] of JP 2020-118960 A can be added.

[0116] [ka]

[0117] [ka] (In the formula, R 204 , R 205 , R 206 , and R 207each represents a linear, branched, or cyclic alkyl group, alkenyl group, oxoalkyl group, or oxoalkenyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 20 carbon atoms, or an aralkyl group or aryloxoalkyl group having 7 to 12 carbon atoms, and some or all of the hydrogen atoms in these groups may be substituted with an alkoxy group or the like. 205 and R 206 may form a ring, and when a ring is formed, R 205 and R 206 A represents an alkylene group having 1 to 6 carbon atoms. - represents a non-nucleophilic counter ion. 208 , R 209 , R 210 , and R 211 is R 204 , R 205 , R 206 , and R 207 R is the same as R, but may also be a hydrogen atom. 208 and R 209 , or R 208 , R 209 and R 210 may form a ring, and when a ring is formed, R 208 and R 209 or R 208 , R 209 and R 210 represents an alkylene group having 3 to 10 carbon atoms.

[0118] The crosslinking catalysts (Xc-1), (Xc-2), (Xc-3), (Xc-4), and / or (Xc-10) can be used singly or in combination of two or more. The amount of the crosslinking catalyst added is preferably 0.01 to 50 parts by mass, more preferably 0.1 to 40 parts by mass, per 100 parts by mass of the base polymer (for example, the thermally crosslinkable polysiloxane (Sx) obtained by the above method).

[0119] [Other ingredients] The silicon-containing hard mask film-forming composition used in the present invention may further contain the following raw materials.

[0120] (acid generator) The silicon-containing hard mask film-forming composition may further contain one or more acid generators. Any acid generator that functions as an acid precursor, such as a thermal acid generator, a photoacid generator, or an acid multiplier, may be used. In the present invention, however, it is preferred that the acid generator used is a sulfonium salt, which is a photoacid generator that generates an acid upon the action of high-energy rays. Specifically, materials described in paragraphs

[0061] to

[0085] of JP 2007-199653 A can be added, but are not limited thereto.

[0121] The acid generators can be used alone or in combination of two or more. When an acid generator is added, the amount added is preferably 0.05 to 50 parts, more preferably 0.1 to 10 parts, per 100 parts of the thermally crosslinkable polysiloxane.

[0122] (Crosslinking agent) A crosslinking agent can be further added to the silicon-containing hard mask film-forming composition to further improve thermosetting properties. The crosslinking agent is not particularly limited, and various known crosslinking agents can be widely used. Examples include melamine-based crosslinking agents, glycoluril-based crosslinking agents, benzoguanamine-based crosslinking agents, urea-based crosslinking agents, β-hydroxyalkylamide-based crosslinking agents, isocyanurate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, epoxy-based crosslinking agents, and phenol-based crosslinking agents. The above crosslinking agents can be used alone or in combination of two or more. When a crosslinking agent is added, the amount added is preferably 5 to 50 parts, more preferably 10 to 40 parts, and even more preferably 10 to 30 parts, per 100 parts of the silicon-containing hard mask film-forming composition.

[0123] (organic acid) In order to improve the stability of the silicon-containing hard mask film-forming composition, it is preferable to add a monovalent or divalent or higher organic acid having 1 to 30 carbon atoms. Examples of the acid to be added in this case include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, stearic acid, linoleic acid, linolenic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, trifluoroacetic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, oxalic acid, malonic acid, methylmalonic acid, ethylmalonic acid, propylmalonic acid, butylmalonic acid, dimethylmalonic acid, diethylmalonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and citric acid. Particularly preferred are oxalic acid, maleic acid, formic acid, acetic acid, propionic acid, citric acid, etc. To maintain stability, two or more acids may be mixed and used.

[0124] The amount of organic acid added is 0.001 to 25 parts by mass, preferably 0.01 to 15 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the thermally crosslinkable polysiloxane contained in the composition for forming a silicon-containing hard mask film.

[0125] Alternatively, the organic acid may be added so that the pH of the silicon-containing hard mask film-forming composition is preferably 0≦pH≦7, more preferably 0.3≦pH≦6.5, and even more preferably 0.5≦pH≦6.

[0126] (solvent) The silicon-containing hard mask film-forming composition may further contain a coating solvent to improve coating properties.

[0127] The solvent used as the coating solvent for the silicon-containing hard mask film-forming composition is preferably the organic solvent used in producing the silicon-containing compound as described above, and it is particularly preferred to use monoalkyl ethers such as ethylene glycol, diethylene glycol, and triethylene glycol, and monoalkyl ethers such as propylene glycol and dipropylene glycol. Specifically, an organic solvent selected from propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol monopropyl ether, and ethylene glycol monopropyl ether is preferred, and can also be used for additional dilution as needed.

[0128] In addition to the above solvents, known stabilizing solvent components such as water can also be added. In order to form a silicon oxide-based material layer having a thickness of 1 to 10 nm on a 152 mm (6 inch) square photomask blank, the amount of the total solvents including water used is preferably 1,000 to 250,000 parts by mass, and particularly preferably 10,000 to 200,000 parts by mass, per 100 parts by mass of the thermally crosslinkable polysiloxane.

[0129] (stabilizer) Furthermore, a stabilizer can be added to the silicon-containing hard mask film-forming composition. A monohydric, dihydric, or polyhydric alcohol having a cyclic ether as a substituent can be added as the stabilizer. In particular, the addition of a stabilizer described in paragraphs

[0181] and

[0182] of JP 2009-126940 A can improve the stability of the silicon-containing hard mask film-forming composition.

[0130] The amount of stabilizer used is preferably 0 to 25 parts by mass, particularly preferably 0 to 5 parts by mass, per 100 parts by mass of the thermally crosslinkable polysiloxane (Sx) that is the base polymer, but when added, 0.5 part by mass or more is preferred.

[0131] (surfactant) Furthermore, if necessary, a surfactant can be added to the composition, specifically, the materials described in paragraph

[0185] of JP-A-2009-126940 can be added as such a surfactant.

[0132] The amount of surfactant used is preferably 0 to 10 parts by mass, and particularly preferably 0 to 5 parts by mass, per 100 parts by mass of the thermally crosslinkable polysiloxane (Sx) that is the base polymer.

[0133] [Photoresist film] A photoresist film is formed on the silicon-containing hard mask film. The resist used here is selected depending on the pattern exposure method. To form a fine pattern using the photomask blank of the present invention, a method using electron beam exposure is generally used, so a chemically amplified electron beam resist using an aromatic resin is generally used. This resist is either positive or negative, depending on the type of pattern. This resist film is irradiated with an electron beam in a pattern, and then subjected to a predetermined post-irradiation heating and development process depending on the resist, to obtain a resist pattern.

[0134] The photomask blanks of the present invention described above contain a silicon-containing hard mask film useful as a hard mask film, allowing for highly accurate transfer of a fine resist pattern to an absorber layer. Furthermore, since the silicon-containing hard mask film can be formed at a temperature range of 50°C to 180°C, the transfer accuracy of the resist pattern can be improved without inducing interlayer mixing of the multilayer reflective film layer. In other words, by using the photomask blanks of the present invention, a photomask can be provided that includes an absorber layer on which a fine pattern is formed with high accuracy without degrading the reflectivity of EUV light. In other words, the photomask blanks of the present invention are photomask blanks that include a silicon-containing hard mask film that can function as a hard mask when processing the absorber layer by dry etching and can also contribute to improving the resolution of the resist pattern.

[0135] <Photomask blank manufacturing method> The method for producing a photomask blank of the present invention includes the steps of: providing a substrate; forming a multilayer reflective film layer that reflects EUV light on the substrate; forming an absorber layer on the multilayer reflective film layer to absorb the EUV light; a step of directly or indirectly applying a silicon-containing hard mask film-forming composition onto the absorber layer, the composition being cured at a temperature of 50°C or higher and 180°C or lower, to obtain a coating film, and curing the coating film at a temperature of 50°C or higher and 180°C or lower, to form a silicon-containing hard mask film; forming a photoresist film on the silicon-containing hard mask film; Includes:

[0136] The multilayer reflective film layer, any protective film, absorber layer, any first layer of the hard mask (etching mask film), and any conductive film, each of which has been described above, can be deposited by, for example, ion beam sputtering or magnetron sputtering.

[0137] The silicon-containing hard mask film is formed by applying a silicon-containing hard mask film-forming composition (e.g., the silicon-containing hard mask film-forming composition) that cures at a temperature of 50°C or higher and 180°C or lower directly or indirectly onto an absorber layer by, for example, spin coating to obtain a coating film, and then curing the coating film at a temperature of 50°C or higher and 180°C or lower.

[0138] After forming a coating film by spin coating or the like, the film is baked to evaporate the organic solvent and cause curing. The baking temperature is 50 to 180°C, more preferably 80 to 170°C, and even more preferably 100 to 150°C. The baking time is preferably 10 to 3,600 seconds, more preferably 300 to 2,400 seconds, and even more preferably 600 to 1,200 seconds.

[0139] Under such baking conditions, a cured film of the silicon-containing hard mask film containing Si-O-Si crosslinks at a sufficient density can be formed directly or indirectly on the absorber layer without disturbing the periodic structure of the multilayer reflective film formed below the silicon-containing hard mask film, thereby achieving high etching resistance against chlorine-based dry etching conditions.

[0140] The thickness of the silicon-containing hard mask film depends on the thickness of the resist film formed on the upper layer and the thickness of the first layer of the hard mask film on the lower layer, but is preferably 1 to 50 nm, more preferably 5 to 30 nm, and particularly preferably 10 to 25 nm. Such a thickness range provides sufficient etching resistance, allowing the resist pattern to be transferred to the absorber layer or the first layer of the hard mask film with high precision.

[0141] The lower limit of the silicon content in the silicon-containing hard mask film is preferably 5% or more, more preferably 10% or more, and even more preferably 30% or more. A film containing silicon at such a ratio has excellent curability, making it possible to more reliably provide a silicon-containing hard mask film that cures at temperatures of 50°C or more and 180°C or less. In addition, high etching resistance can be obtained under chlorine-based dry etching conditions.

[0142] The upper limit of the silicon content in the silicon-containing hard mask film is preferably 50% or less, more preferably 45% or less. If the film contains silicon at such a rate, for example, after dry etching the Cr-containing hard mask, the silicon-containing hard mask film remaining on the Cr-containing hard mask film pattern can be easily removed.

[0143] The photoresist film can be formed by a coating method such as spin coating.

[0144] The photomask blanks of the present invention described above can be manufactured by the method for manufacturing a photomask blank of the present invention described above. However, the photomask blanks of the present invention can also be manufactured by methods other than the manufacturing method described above.

[0145] <Photomask blank processing method> The method for processing photomask blanks of the present invention includes the steps of: (i-1) a step of irradiating the photomask blank of the present invention with an electron beam and then developing it with a developer to form a photoresist pattern on the photoresist film; (i-2) forming the silicon-containing film pattern on the silicon-containing hard mask film by etching using the photoresist pattern as a mask; (i-3) directly or indirectly processing the absorber layer by etching using the silicon-containing film pattern as a mask; The present invention is characterized by comprising:

[0146] This photomask blank processing method uses a silicon-containing hard mask film, which has better dry etching resistance to chlorine-based gases than a photoresist film, as a hard mask, allowing the resist pattern to be transferred to the absorber layer of the photomask blank with high accuracy. Furthermore, since the silicon-containing hard mask film can be formed at a temperature range of 50°C to 180°C, the transfer accuracy of the resist pattern can be improved without inducing interlayer mixing in the multilayer reflective film layer. In other words, the photomask blank processing method of the present invention can provide a photomask including an absorber layer on which a fine pattern is formed with high accuracy without degrading the reflectivity of EUV light.

[0147] A specific example of the method for processing the photomask blanks of the present invention will be described below.

[0148] First, a substrate is formed; a multilayer reflective film layer is formed on the substrate, the multilayer reflective film layer reflecting the exposure light, which is EUV light; a protective film is formed on the multilayer reflective film layer to protect the multilayer reflective film layer; an absorber layer is formed on the protective film to absorb the exposure light; and a Cr-containing hard mask film is formed on the absorber layer, the hard mask film functioning as the first layer of a hard mask when the absorber layer is patterned by dry etching.

[0149] Next, the silicon-containing hard mask film-forming composition described above is applied to the Cr-containing hard mask film and baked at a temperature of 50°C to 180°C to form a cured silicon-containing hard mask film. That is, the silicon-containing hard mask film is formed directly or indirectly on the absorber layer. Next, a photoresist film is formed on the silicon-containing hard mask film. This results in a photomask blank.

[0150] The resist film of this photomask blank is irradiated with an electron beam in a pattern, and then undergoes heating and development steps to form a resist pattern.

[0151] The resulting resist pattern is first transferred to a silicon-containing hard mask film by dry etching. Dry etching conditions can be fluorine-based dry etching using commonly used fluorine-containing gases. Examples of fluorine-containing gases include fluorine gas, carbon- and fluorine-containing gases such as CF4, CHF3, and C2F6, and sulfur- and fluorine-containing gases such as SF6. Furthermore, mixed gases of fluorine-free gases such as helium and nitrogen and fluorine-containing gases may also be used. Furthermore, gases such as oxygen may be added as needed.

[0152] Next, the photoresist is stripped or left on the silicon-containing hard mask film, and the resulting silicon-containing hard mask film pattern is used as a hard mask to transfer the pattern to a Cr-containing hard mask film. The dry etching used here can be chlorine-based dry etching. For example, commonly used chlorine-based dry etching containing oxygen can be used. The dry etching conditions include a mixture of chlorine gas and oxygen gas (Cl2 gas:O2 gas) at a volumetric flow ratio of 1:2 to 20:1, optionally containing an inert gas such as helium. Because silicon-containing hard mask films have higher resistance to chlorine-based dry etching than resist films, using a silicon-containing hard mask film as a hard mask allows the resist pattern to be transferred to a Cr hard mask with high accuracy.

[0153] The Cr hard mask film pattern is used as a hard mask to transfer the pattern to the absorber layer. The dry etching used here can be fluorine-based dry etching using commonly used fluorine-containing gas conditions. Examples of fluorine-containing gases include fluorine gas, carbon- and fluorine-containing gases such as CF4, CHF3, and C2F6, and sulfur- and fluorine-containing gases such as SF6. Furthermore, a mixed gas of a fluorine-free gas such as helium or nitrogen with a fluorine-containing gas may also be used. Furthermore, a gas such as oxygen may be added as needed. The silicon-containing hard mask film remaining on the Cr hard mask film can be removed by the fluorine-based dry etching. Furthermore, wet etching may be performed before the fluorine-based dry etching, as with a general SOG film.

[0154] The Cr hard mask film remaining on the absorber layer can be removed by chlorine-based dry etching, which is resistant to the protective film formed on the multilayer reflective coating.

[0155] Although the above example shows the case where a silicon-containing hard mask film is indirectly formed on the absorber layer via a Cr hard mask film, the present invention also allows the silicon-containing hard mask film to be formed directly on the absorber layer, in which case the silicon-containing hard mask film pattern can be used as a mask for etching the absorber layer. [Example]

[0156] The present invention will be specifically explained below with reference to Synthesis Examples, Examples, and Comparative Examples, but the present invention is not limited to these descriptions. In the following examples, % indicates mass %, and the molecular weight Mw is the weight average molecular weight in terms of polystyrene measured by GPC.

[0157] [Synthesis Example 1] A mixture of 30.6 g of compound (101), 38.1 g of compound (102), and 5.9 g of compound (110) was added to a mixture of 120 g of methanol, 0.1 g of 10% nitric acid, and 60 g of deionized water, and the mixture was maintained at 40°C for 12 hours to allow hydrolysis and condensation. After completion of the reaction, 600 g of propylene glycol ethyl ether (PGEE) was added, and the water and by-product alcohol used in the hydrolysis and condensation were distilled off under reduced pressure to obtain 440 g of a PGEE solution of polysiloxane compound 1 (compound concentration 10%). The polystyrene-equivalent molecular weight of polysiloxane compound 1 was measured, and found to be Mw = 2,900.

[0158] [Synthesis Examples 2 to 8] [Synthesis Example 2] to [Synthesis Example 8] were carried out using the monomers shown in Table 1 under the same conditions as in Synthesis Example 1, to obtain the respective target products (polysiloxane compounds 2 to 8).

[0159] [Table 1]

[0160] The compounds used in the synthesis examples are shown below. PhSi(OCH3)3...Compound (100) CH3Si(OCH3)3...Compound (101) Si(OCH3)4...Compound (102)

[0161] [ka]

[0162] [Synthesis Example 9] 1400 g of ethanol, 700 g of ultrapure water, and 50 g of 25% tetramethylammonium hydroxide were mixed and heated to 40°C under a nitrogen atmosphere to form a homogeneous solution. A mixture of 138.6 g of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 37.2 g of phenyltrimethoxysilane was slowly added dropwise to this homogeneous solution, and the reaction was allowed to proceed at 40°C for 2 hours. After completion of the reaction, 35 g of acetic acid was added to the solution to quench the reaction, and the ethanol was distilled off under reduced pressure. 2000 ml of ethyl acetate was added to the distilled solution, and the aqueous layer was separated. The organic layer was washed twice with 400 ml of ultrapure water, after which 1000 g of PGMEA (propylene glycol monomethyl ether acetate) was added, and the water and low-boiling point solvents were distilled off to recover 600 g of PGMEA solution of polysiloxane compound 9 (compound concentration 20%). The polystyrene-equivalent molecular weight of polysiloxane compound 9 was measured to be Mw = 2800.

[0163] [Preparation of silicon-containing hard mask film-forming composition] The polysiloxane compounds 1 to 9 obtained in the above synthesis examples, crosslinking catalysts (XLC-1 to 3), acid generators (AG1 to 4), crosslinking agent (XL1), organic solvent, and water were mixed in the proportions shown in Table 2, and each mixture was filtered through a 0.1 μm fluororesin filter to prepare silicon-containing underlayer film-forming composition solutions, designated UDL-1 to 18, respectively.

[0164] [Table 2]

[0165] The crosslinking catalysts used were as follows: XLC-1: Triphenylsulfonium nitrate XLC-2 Mono(triphenylsulfonium) maleate XLC-3···Triethylphenylammonium iodide

[0166] The organic solvents used were as follows: PGEE: Propylene glycol ethyl ether PGMEA: Propylene glycol methyl ether acetate

[0167] The acid generators used are as shown in Table 3 below. [Table 3]

[0168] The crosslinker (XL1) used was as follows: [ka]

[0169] [Solvent resistance evaluation] On a substrate, 40 pairs of 4 nm Si films and 3 nm Mo films were formed, followed by a 3 nm Si layer on the surface to form a multilayer reflective film. A 2.5 nm Ru protective layer and a 70 nm TaN absorber layer were sequentially formed on this multilayer reflective film. One of the silicon-containing hard mask film-forming compositions (UDL-1 to UDL-18) prepared above was applied to this absorber layer, and the resulting coating was baked under the baking conditions listed in Table 4 to obtain a silicon-containing hard mask film. Thus, the composites of Examples 1-1 to 1-20 were obtained.

[0170] The film thickness of the obtained composites of Examples 1-1 to 1-20 from the center to the periphery of the substrate was measured, and the average film thickness (a [nm]) was calculated. Subsequently, PGMEA solvent was dispensed thereon, left for 30 seconds, spin-dried, and baked at 110°C for 600 seconds to evaporate the PGMEA, and then the film thickness (b [nm]) was measured.

[0171] Table 4 below shows the film thicknesses a and b, and the value of (b / a)×100 as an index of solvent resistance.

[0172] [Table 4]

[0173] As shown in Table 4, in Examples 1-1 to 1-20, the residual film ratio ((b / a) x 100) after PGMEA rinsing treatment was 98% or more, indicating that a crosslinking reaction occurred even on the mask blanks, demonstrating sufficient solvent resistance. In particular, Examples UDL-10 to 17, which contained a crosslinking catalyst, showed excellent curing properties and could be processed at a lower baking temperature. Furthermore, in Examples 1-18 to 1-20, it was confirmed that the higher the baking temperature and the longer the baking time, the better the solvent resistance.

[0174] Furthermore, in Examples 1-1 to 1-20, it was confirmed that all of the silicon-containing hard mask film-forming compositions (UDL-1 to 18) prepared above were cured at a temperature of 50°C or higher and 180°C or lower, more specifically, at a temperature of 120°C or higher and 150°C or lower.

[0175] [Reflectance] (Base substrate with multilayer reflective film) On the substrate, 40 pairs of 4 nm Si and 3 nm Mo were formed, and then 3 nm Si was formed on the surface to form a multilayer reflective film. A Ru 2.5 n protective film was formed on this multilayer reflective film. In this way, a standard substrate with a multilayer reflective film was obtained.

[0176] The peak reflectance of EUV light (wavelength 13.5 nm, same below) at an incident angle of 6° on the main surface of this standard multilayer reflective film substrate was measured and found to be 65%.

[0177] Example 2-1 Next, a multilayer reflective film layer and a protective film were formed on the main surface of the above-mentioned mask blank substrate under the same conditions as those for producing the above-mentioned reference multilayer reflective film layer-coated substrate, thereby producing a multilayer reflective film layer-coated substrate of Example 2-1. This multilayer reflective film layer-coated substrate was subjected to a baking treatment at 120°C for 600 seconds, under the conditions at which the solvent resistance of the silicon-containing hard mask film in the above-mentioned examples was 98% or higher. Thus, an evaluation substrate of Example 2-1 was obtained. The peak reflectance of the main surface of this evaluation substrate at an incident angle of 6° to EUV light (wavelength 13.5 nm, the same applies below) was measured and found to be 65%.

[0178] (Example 2-2) An evaluation substrate of Example 2-2 was produced under the same conditions as Example 2-1, except that the baking conditions on the multilayer reflective film layer-coated substrate of Example 2-1 were changed to 150° C. for 600 seconds. The peak reflectance of the main surface of this evaluation substrate was measured at an incident angle of 6° to EUV light (wavelength 13.5 nm, the same applies below), and was found to be 65%.

[0179] (Example 2-3) An evaluation substrate for Example 2-3 was produced under the same conditions as Example 2-1, except that the baking conditions on the multilayer reflective film layer-coated substrate in Example 2-1 were changed to 180° C. for 600 seconds. The peak reflectance of the main surface of this evaluation substrate was measured at an incident angle of 6° to EUV light (wavelength 13.5 nm, the same applies below), and was found to be 64%.

[0180] (Comparative Example 2-1) A mask blank substrate was produced under the same conditions as in Example 2-1, except that the baking conditions on the multilayer reflective film-coated substrate were changed to 200°C for 600 seconds. The peak reflectance of the main surface of this multilayer reflective film-coated substrate at an incident angle of 6° to EUV light (wavelength 13.5 nm, the same applies below) was measured and found to be 62%. Furthermore, when a cross section of the obtained multilayer reflective film was observed with a transmission electron microscope (TEM), an interdiffusion layer of Si and Mo was observed.

[0181] From the above results, it was found that the photomask blanks of the present invention contain a silicon-containing hard mask film that is a cured product of a silicon-containing hard mask-forming composition that cures at a temperature of 50°C or higher and 180°C or lower, and therefore do not require baking at temperatures exceeding 180°C during silicon-containing hard mask film formation. It was also found that, as demonstrated in Examples 2-1 to 2-3, a silicon-containing hard mask film useful as a hard mask can be formed at temperatures of 50°C or higher and 180°C or lower without degrading the EUV light reflectance of the multilayer reflective film layer. On the other hand, it was found that, unlike the present invention, when a silicon-containing hard mask-forming composition that requires a baking temperature of more than 180°C for the silicon-containing hard mask film is used, interlayer mixing of the multilayer reflective film layer occurs, resulting in a degradation of the EUV light reflectance.

[0182] [Exposure evaluation] (Examples 3-1 to 3-24) On the substrate, 40 pairs of 4 nm Si films and 3 nm Mo films were formed, followed by a 3 nm Si layer on the surface to form a multilayer reflective film. A 2.5 nm Ru protective film and a 70 nm TaN absorber layer were then formed on this multilayer reflective film. A 6 nm thick CrN film was then formed on this absorber layer to form the first layer of the hard mask film.

[0183] One of the silicon-containing hard mask film-forming compositions (UDL-1 to 18) prepared above was applied onto the CrN film by spin coating, and baked under the baking conditions listed in Table 5 to form a silicon-containing hard mask layer (silicon oxide material film) with a thickness of 20 nm as the second layer of the hard mask.

[0184] Next, a photoresist film of SEBP-504G, a chemically amplified resist solution for electron beams manufactured by Shin-Etsu Chemical Co., Ltd., was formed to a thickness of 90 nm or 60 nm on the substrate on which the silicon-containing hard mask layer was formed using a spin coater. Thus, photomask blanks for each example were produced.

[0185] Next, the photoresist film of each photomask blank was exposed using an electron beam exposure system (EBM5000, manufactured by NuFLARE, accelerating voltage 50 keV), baked at 110°C for 10 minutes (PEB: post exposure bake), and developed in a 2.38% by mass aqueous solution of tetramethylammonium hydroxide, thereby obtaining a positive photoresist pattern containing a 100 nm line pattern. Note that the above exposure was performed at the optimal exposure dose (sensitivity: Eop) that resolved the top and bottom of the resulting 100 nm line and space at a 1:1 ratio.

[0186] The line edge roughness of the resist pattern was measured. The line edge roughness was measured by detecting 80 edges on each of the 32 edges of the 100 nm LS pattern using an SEM (E3640 manufactured by Advantest Corporation), and the triple value (3σ) of the standard deviation (σ) was calculated to obtain the LER (nm).

[0187] Subsequently, using the photoresist pattern as an etching mask, the mask blanks were processed in the following manner.

[0188] First, using the photoresist pattern as a mask, the silicon-containing hard mask film exposed from the resist pattern was dry etched and patterned using a dry etching apparatus under the following fluorine-based dry etching conditions. [Silicon-containing film etching conditions] RF1(RIE):CW 54V RF2(ICP):CW 325W Pressure: 5mTorr SF6:18sccm O2: 45sccm Etching time: 1 min

[0189] Next, the photoresist pattern was stripped off with oxygen plasma, and then the exposed Cr hard mask film was dry-etched using the patterned silicon-containing hard mask film (silicon-containing film pattern) as a mask under the following oxygen-containing chlorine-based dry etching conditions, thereby patterning the film.

[0190] [Etching conditions for Cr hard mask film] RF1(RIE):CW 10W RF2 (ICP): CW 300W Pressure: 5mTorr Cl2: 150sccm O2: 50sccm He:10sccm Etching time: 1 min

[0191] Next, the exposed TaN absorber layer film was dry etched and patterned using the patterned Cr hard mask film as a mask under Etching Condition-2, which is a succession of Etching Condition-1.

[0192] [TaN film etching conditions-1] RF1(RIE):CW 54W RF2(ICP):CW 325W Pressure: 5mTorr SF6:18sccm He:130sccm Etching time: 10 seconds

[0193] [TaN film etching conditions-2] RF1(RIE):CW 7.6W RF2 (ICP): CW 300W Pressure: 5mTorr Cl2: 150sccm He:10sccm Etching time: 5 min

[0194] (Comparative Examples 3-1 and 3-2) Photomask blanks were prepared in the same manner as in Example 3-1 or 3-14, except that a photoresist film having a film thickness shown in Table 5 was directly formed on the CrN film without forming a silicon-containing hard mask layer, and these photomask blanks were processed in the same manner as in Example 3-1 or 3-14.

[0195] The line edge roughness (LER) of the patterned structures obtained by the etching described above in Examples 3-1 to 3-24 and Comparative Examples 3-1 and 3-2 was measured. The LER (nm) was calculated by detecting 80 edges on each of the 32 edges of a 100 nm LS pattern using an SEM (Advantest E3640). The standard deviation (σ) was tripled (3σ) to obtain the LER. A smaller value indicates better performance. The cross-sectional shape (pattern shape) was observed using an electron microscope (Hitachi High-Technologies S-4800). A good result was obtained when no footing or undercut was observed, and a poor result was obtained when obvious footing or undercut was observed. The results are shown in Table 5.

[0196] [Table 5]

[0197] As shown in Table 5, the photomask blanks of Examples 3-1 to 3-24, which contained a silicon-containing hard mask film of the present invention, exhibited better resist pattern edge roughness and superior pattern shapes after etching compared to Comparative Examples 3-1 and 3-2, which did not contain a silicon-containing hard mask film. Examples 3-1 to 3-8, which used polysiloxanes (Compounds 1 to 7) containing organic groups having one or more carbon-oxygen single bonds or carbon-oxygen double bonds, exhibited better resist pattern edge roughness. This is presumably due to the excellent adhesion to the resist pattern. Furthermore, Examples 3-11 to 3-23, which used silicon-containing hard mask film-forming compositions (UDL-10 to 17) containing a crosslinking catalyst, exhibited even better resist pattern edge roughness and also exhibited better post-etching edge roughness compared to compositions not containing a crosslinking catalyst. This is presumably due to the improved denseness of the silicon-containing hard mask film due to the addition of a crosslinking catalyst.

[0198] As shown in Comparative Example 3-2, when the resist film thickness was set to 60 nm, deterioration of the cross-sectional shape was confirmed, resulting in deterioration of the LER. However, in Examples 3-14 and 3-19, which included a silicon-containing hard mask film, no deterioration of the cross-sectional shape was observed, and good LER was obtained. This is presumably due to the good adhesion between the silicon-containing hard mask film and the resist film.

[0199] As described above, the photomask blank of the present invention contains a silicon-containing hard mask film useful as a hard mask film, and therefore can transfer a fine resist pattern to an absorber layer with high accuracy. Furthermore, the silicon-containing hard mask film-forming composition used in the present invention can be cured at a temperature range of 50°C to 180°C, thereby improving the transfer accuracy of the resist pattern without inducing interlayer mixing in the multilayer reflective film. In other words, the present invention can provide a photomask blank that can provide a photomask on which a fine pattern is formed with high accuracy without degrading the reflectivity of EUV light.

[0200] The present specification includes the following aspects. [1] A photomask blank, A substrate; a multilayer reflective film layer formed on the substrate and reflecting EUV light; an absorber layer formed on the multilayer reflective film layer to absorb the EUV light; a silicon-containing hard mask film formed directly or indirectly on the absorber layer; a photoresist film formed on the silicon-containing hard mask film; Equipped with The photomask blanks are characterized in that the silicon-containing hard mask film is a cured product of a silicon-containing hard mask film-forming composition that is cured at a temperature of 50°C or higher and 180°C or lower. [2] The photomask blank according to [1], wherein the composition for forming a silicon-containing hard mask film contains a silicon-containing compound having at least one of a repeating unit represented by the following general formula (Sx-1), a repeating unit represented by the following general formula (Sx-2), and a partial structure represented by the following general formula (Sx-3): [ka] (In the formula, R a , R b , and R c are each a monovalent organic group having 1 to 30 carbon atoms, which may be the same or different. [3] In the above formulas (Sx-1) to (Sx-3), R a ~R c At least one of the above is an organic group having one or more carbon-oxygen single bonds or carbon-oxygen double bonds. [4] The photomask blank according to any one of [1] to [3], wherein the silicon-containing hard mask film-forming composition further contains a crosslinking catalyst. [5] The photomask blank according to [4], wherein the crosslinking catalyst is a sulfonium salt, an iodonium salt, a phosphonium salt, an ammonium salt, an alkali metal salt, or a polysiloxane having any of a sulfonium salt, an iodonium salt, a phosphonium salt, and an ammonium salt as part of its structure. [6] A method for processing photomask blanks, comprising: (i-1) A step of irradiating the photomask blank according to any one of [1] to [5] with an electron beam and then developing it with a developer to form a photoresist pattern on the photoresist film; (i-2) forming the silicon-containing film pattern on the silicon-containing hard mask film by etching using the photoresist pattern as a mask; (i-3) directly or indirectly processing the absorber layer by etching using the silicon-containing film pattern as a mask; A method for processing a photomask blank, comprising: [7] A method for manufacturing a photomask blank, comprising: providing a substrate; forming a multilayer reflective film layer that reflects EUV light on the substrate; forming an absorber layer on the multilayer reflective film layer to absorb the EUV light; a step of directly or indirectly applying a silicon-containing hard mask film-forming composition onto the absorber layer, the composition being cured at a temperature of 50°C or higher and 180°C or lower, to obtain a coating film, and curing the coating film at a temperature of 50°C or higher and 180°C or lower, to form a silicon-containing hard mask film; forming a photoresist film on the silicon-containing hard mask film; A method for producing a photomask blank, comprising:

[0201] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0202] 1...substrate, 2...multilayer reflective film layer, 3...protective film, 4...absorber layer, 5...first layer of hard mask film, 6...silicon-containing hard mask film (second layer of hard mask), 7...photoresist film, 101...photomask blank.

Claims

1. A photomask blank, A substrate; a multilayer reflective film layer formed on the substrate and reflecting EUV light; an absorber layer formed on the multilayer reflective film layer to absorb the EUV light; a silicon-containing hard mask film formed directly or indirectly on the absorber layer; a photoresist film formed on the silicon-containing hard mask film; Equipped with The photomask blanks are characterized in that the silicon-containing hard mask film is a cured product of a silicon-containing hard mask film-forming composition that is cured at a temperature of 50°C or higher and 180°C or lower.

2. The photomask blank according to claim 1, wherein the composition for forming a silicon-containing hard mask film contains a silicon-containing compound having at least one of a repeating unit represented by the following general formula (Sx-1), a repeating unit represented by the following general formula (Sx-2), and a partial structure represented by the following general formula (Sx-3): 【Chemistry 1】 (In the formula, R ａ , R ｂ , and R ｃ are each a monovalent organic group having 1 to 30 carbon atoms, which may be the same or different.

3. In the above formulas (Sx-1) to (Sx-3), R ａ ~R ｃ 3. The photomask blank according to claim 2, wherein at least one of the above is an organic group having one or more carbon-oxygen single bonds or carbon-oxygen double bonds.

4. 2. The photomask blank according to claim 1, wherein the silicon-containing hard mask film-forming composition further contains a crosslinking catalyst.

5. 5. The photomask blank according to claim 4, wherein the crosslinking catalyst is a sulfonium salt, an iodonium salt, a phosphonium salt, an ammonium salt, an alkali metal salt, or a polysiloxane having any one of a sulfonium salt, an iodonium salt, a phosphonium salt, and an ammonium salt as part of its structure.

6. A method for processing photomask blanks, comprising: (i-1) a step of irradiating the photomask blank according to any one of claims 1 to 5 with an electron beam, and then developing the photomask blank with a developer to form a photoresist pattern on the photoresist film; (i-2) forming the silicon-containing film pattern on the silicon-containing hard mask film by etching using the photoresist pattern as a mask; (i-3) directly or indirectly processing the absorber layer by etching using the silicon-containing film pattern as a mask; A method for processing a photomask blank, comprising:

7. A method for manufacturing a photomask blank, comprising: providing a substrate; forming a multilayer reflective film layer that reflects EUV light on the substrate; forming an absorber layer on the multilayer reflective film layer to absorb the EUV light; a step of directly or indirectly applying a silicon-containing hard mask film-forming composition onto the absorber layer, the composition being cured at a temperature of 50°C or higher and 180°C or lower, to obtain a coating film, and curing the coating film at a temperature of 50°C or higher and 180°C or lower, to form a silicon-containing hard mask film; forming a photoresist film on the silicon-containing hard mask film; A method for producing a photomask blank, comprising:

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